The incorporation of biobased monomers into polymer structures offers the possibility to develop materials in a more climate-friendly way. By using biogenic monomers, the carbon footprint of polymer production can be reduced. In the recent years IPF has developed polyesters with specific biobased units for integrating specific functions. Examples will be given for liquid crystalline polyesters with bio-based vanillic acid units allowing blending with lignin fraction.¹ The resulting melt-spun fibers are excellent precursor fibers for carbon fibers. In addition, incorporation of unsaturated ferulic acid units allows stabilization of fibers by electron beam irradaition, increasing mechanical strength.²

In addition, we present the successful preparation of novel polyester extrusion foams from dilinoleic derivatives for moulded parts and insulations.³ The synthesis of the copolyesters was performed successfully to comparably high molar masses by transesterification polymerization in the melt. PBT-based terpolyesters with dilinoleic derivatives were prepared to introduce long alkyl chains as side chains into the polyester basic structure. This approach allows to incorporate short-chain branches in a very defined manner to understand better the requirements for successful foaming. The structure of the terpolymers and their material properties were investigated in detail in order to derive structure-property relationships. The results show that the short-chain branches change the shape of the polymer coil and the general behavior in solution, in solid and in the molten state. The incorporation of both types of dilinoleic derivatives results in an increase of solubility, a reduction of glass transition temperatures and a reduced crystallinity. Most importantly, the rheological behavior is altered, especially the elongational rheology towards strain hardening. This has a strong positive influence on the properties of the resulting foam (density, morphology, cell density, weldability. Interestingly, PBT can be replaced in part by polybutylenefuranoate, a fully bio-based polyester with reactive functions for foam stabilization.

 References

1. D. Pospiech, A. Korwitz, K. Eckstein, H. Komber, D. Jehnichen, A. Lederer, K. Arnhold, M. Göbel, M. Bremer, A. Hoffmann, St. Fischer, A. Werner, Th. Walther, H. Brünig, B. Voit, J. Applied Polym, Sci., 2019, 136, No 48257.
2. D. Pospiech, A. Korwitz, H. Komber, D. Jehnichen, K. Arnhold, H. Brünig, H. Scheibner, M. T. Müller, B. Voit, Polym. Chem., 2021, 12, 5139-5148.
3. Ch. Mielke, J. Kuhnigk, D. Pospiech, H. Komber, R. Boldt, A. Lederer, M. El Fray, T. Standau, H. Ruckdäschel, V. Altstädt, B. Voit, Macromol. Mater. Eng., 2022, 307, 2200208.